The preparation of siloxane-oxyalkylene copolymers by the hydrosilation reaction of an organohydrogensiloxane and an olefinically substituted polyoxyalkylene is well known and reported in the literature. The hydrosilation reaction is typically performed in a low molecular weight volatile hydrocarbon solvent such as benzene, toluene, xylene or isopropanol so as to aid in handling the reactants, to moderate an exothermic reaction or to promote the solubility of the reactants.
Less typically, the hydrosilation reaction between the organohydrogenpolysiloxane reactant and the olefinically substituted polyoxyalkylene reactant may be conducted without a solvent such as disclosed in U.S. Pat. No. 3,980,688 or conducted in an oxygen containing solvent such as an ether, a polyether, or a lower or higher molecular weight alcohol.
For instance, U.S. Pat. Nos. 3,280,160 and 3,401,192 disclose the preparation of copolymers in n-butylether and in a 50/50 mixture of isopropyl alcohol/toluene, respectively. Also in U.S. Pat. No. 4,122,029 the use of isopropyl alcohol is disclosed and in U.S. Pat. No. 3,518,288 the patentee teaches the use of n-propanol/toluene as a suitable solvent for the preparation of siloxane-oxyalkylene copolymers.
In the majority of the aforementioned processes, the hydrocarbon solvent is removed after the hydrosilation reaction is completed, since in most cases, the solvent is too flammable, toxic or otherwise detrimental to the final product or further processing steps in which the copolymer is utilized. Thus, in the processes disclosed in most of the above patents the solvent was removed from the reaction product after completion of the hydrosilation. A few instances have been reported in the literature where for one reason or another it was not necessary nor desirable to separate the copolymer from the reaction medium. For example, U.S. Pat. No. 4,520,160 disclosed the use of saturated higher alcohols as a reaction solvent which purposely need not be removed from the resulting copolymer when it is used subsequently in personal care compositions as emulsifiers.
U.S. Pat. No. 3,629,308 also disclosed the use of polyethers having a formula R'O(C.sub.3 H.sub.8 O).sub.x H where R' is a lower alkyl group and x has a value of from 1 to 20 as a suitable solvent for the preparation of copolymers. When the resulting siloxane-oxyalkylene is to be used as a stabilizer for urethane foams, the patent teaches that it is not necessary to isolate the copolymer from the solvent but rather to use it as a solution.
In many instances, however, the solvent does not enter into any further reactions but remains in the final product as is, and hence, there is no need for its removal if it does not adversely affect the product. Thus, in some products, such as personal care products it may even be beneficial to have some of the solvent present in the final product. However, if the copolymer is to undergo further reactions before preparation of the final product is complete, its presence might adversely affect such reactions and hence its removal after the hydrosilation step is desired. For example, if one were to use copolymers containing monohydric higher alcohols in urethane foam applications, these alcohols will enter into the urethane reaction and act as reaction chain terminators in a detrimental fashion because they contain only one hydroxyl group. Also as previously indicated, such solvents may be toxic or otherwise undesirable in further processing of the copolymer.
It is therefore an object of the present invention to provide an improved process for the preparation of siloxane-oxyalkylene copolymers. Another object of this invention is to provide a process for the preparation of siloxane-oxyakylene copolymers which are useful in the formulation of urethane foams and wherein it is not necessary to remove the reaction solvent. A further object of the invention is to provide a process for the preparation of urethane foams which have improved flow properties and other desirable features. These and other objects will readily become apparent to those skilled in the art in the light of the teachings contained herein.